diff --git a/drivers/arm/gic/common/gic_common.c b/drivers/arm/gic/common/gic_common.c
index d523772..07ed63d 100644
--- a/drivers/arm/gic/common/gic_common.c
+++ b/drivers/arm/gic/common/gic_common.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2017, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2018, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -302,12 +302,15 @@
 
 void gicd_set_icfgr(uintptr_t base, unsigned int id, unsigned int cfg)
 {
-	unsigned bit_num = id & ((1 << ICFGR_SHIFT) - 1);
+	/* Interrupt configuration is a 2-bit field */
+	unsigned int bit_num = id & ((1 << ICFGR_SHIFT) - 1);
+	unsigned int bit_shift = bit_num << 1;
+
 	uint32_t reg_val = gicd_read_icfgr(base, id);
 
 	/* Clear the field, and insert required configuration */
-	reg_val &= ~(GIC_CFG_MASK << bit_num);
-	reg_val |= ((cfg & GIC_CFG_MASK) << bit_num);
+	reg_val &= ~(GIC_CFG_MASK << bit_shift);
+	reg_val |= ((cfg & GIC_CFG_MASK) << bit_shift);
 
 	gicd_write_icfgr(base, id, reg_val);
 }
diff --git a/drivers/arm/gic/v3/gicv3_helpers.c b/drivers/arm/gic/v3/gicv3_helpers.c
index dee63f1..69c6951 100644
--- a/drivers/arm/gic/v3/gicv3_helpers.c
+++ b/drivers/arm/gic/v3/gicv3_helpers.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2017, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2018, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -232,12 +232,15 @@
  */
 void gicr_set_icfgr0(uintptr_t base, unsigned int id, unsigned int cfg)
 {
-	unsigned bit_num = id & ((1 << ICFGR_SHIFT) - 1);
+	/* Interrupt configuration is a 2-bit field */
+	unsigned int bit_num = id & ((1 << ICFGR_SHIFT) - 1);
+	unsigned int bit_shift = bit_num << 1;
+
 	uint32_t reg_val = gicr_read_icfgr0(base);
 
 	/* Clear the field, and insert required configuration */
-	reg_val &= ~(GIC_CFG_MASK << bit_num);
-	reg_val |= ((cfg & GIC_CFG_MASK) << bit_num);
+	reg_val &= ~(GIC_CFG_MASK << bit_shift);
+	reg_val |= ((cfg & GIC_CFG_MASK) << bit_shift);
 
 	gicr_write_icfgr0(base, reg_val);
 }
@@ -248,12 +251,15 @@
  */
 void gicr_set_icfgr1(uintptr_t base, unsigned int id, unsigned int cfg)
 {
-	unsigned bit_num = id & ((1 << ICFGR_SHIFT) - 1);
+	/* Interrupt configuration is a 2-bit field */
+	unsigned int bit_num = id & ((1 << ICFGR_SHIFT) - 1);
+	unsigned int bit_shift = bit_num << 1;
+
 	uint32_t reg_val = gicr_read_icfgr1(base);
 
 	/* Clear the field, and insert required configuration */
-	reg_val &= ~(GIC_CFG_MASK << bit_num);
-	reg_val |= ((cfg & GIC_CFG_MASK) << bit_num);
+	reg_val &= ~(GIC_CFG_MASK << bit_shift);
+	reg_val |= ((cfg & GIC_CFG_MASK) << bit_shift);
 
 	gicr_write_icfgr1(base, reg_val);
 }
diff --git a/include/drivers/arm/gic_common.h b/include/drivers/arm/gic_common.h
index 001f573..6e953a0 100644
--- a/include/drivers/arm/gic_common.h
+++ b/include/drivers/arm/gic_common.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2017, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2018, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -29,9 +29,9 @@
 /* Constant to indicate a spurious interrupt in all GIC versions */
 #define GIC_SPURIOUS_INTERRUPT		1023
 
-/* Interrupt configurations */
-#define GIC_INTR_CFG_LEVEL		0
-#define GIC_INTR_CFG_EDGE		1
+/* Interrupt configurations: 2-bit fields with LSB reserved */
+#define GIC_INTR_CFG_LEVEL		(0 << 1)
+#define GIC_INTR_CFG_EDGE		(1 << 1)
 
 /* Constants to categorise priorities */
 #define GIC_HIGHEST_SEC_PRIORITY	0x0